There has been a major effort in recent years, with significant success, to discover new drug compounds that act by stimulating certain key aspects of the immune system, as well as by suppressing certain other aspects. These compounds, referred to herein as immune response modifiers (IRMs), appear to act through immune system mechanisms known as toll-like receptors to induce selected cytokine biosynthesis. They may be useful for treating a wide variety of diseases and conditions. For example, certain IRMs may be useful for treating viral diseases (e.g., human papilloma virus, hepatitis, herpes), neoplasias (e.g., basal cell carcinoma, squamous cell carcinoma, actinic keratosis, melanoma), and TH2-mediated diseases (e.g., asthma, allergic rhinitis, atopic dermatitis), and are also useful as vaccine adjuvants.
Many of the IRM compounds are small organic molecule imidazoquinoline amine derivatives (see, e.g., U.S. Pat. No. 4,689,338), but a number of other compound classes are known as well (see, e.g., U.S. Pat. Nos. 5,446,153, 6,194,425, and 6,110,929) and more are still being discovered.
One of these IRM compounds, known as imiquimod, has been commercialized in a topical formulation, ALDARA, for the treatment of actinic keratosis, basal cell carcinoma, or anogenital warts associated with human papillomavirus.
Pharmaceutical formulations containing IRM compounds are disclosed in U.S. Pat. Nos. 5,238,944; 5,939,090; and 6,425,776; European Patent 0 394 026; and U.S. Patent Publication 2003/0199538.
Although some of the beneficial effects of IRMs are known, the ability to provide therapeutic benefit via topical application of an IRM compound for treatment of a particular condition at a particular location may be hindered by a variety of factors. These factors include: irritation of the skin to which the formulation is applied; formulation wash away; insolubility of the IRM compound in the formulation; chemical degradation of the IRM compound and/or other ingredients, physical instability of the formulation (e.g., separation of components, thickening, precipitation/agglomerization of active ingredient, and the like); poor permeation; and undesired systemic delivery of topical IRM formulations if not intended to be transdermal.
Accordingly, there is a continuing need for new and/or improved IRM formulations.